Synthesis and Structure of l,2,3-Tritellura-[3]ferrocenophane

We now report on l,2,3-tritellura-[3]ferrocenophane (5) which contains the Te3 chain as part of a cyclic structure: pared by tellurium insertion into the cyclopentadienyl-lithium bonds of l,l'-dilithioferrocene. Small amounts of 5 are already formed if a THF solution of the insertion product {Fe(C5H4TeLi)2} is stirred in the presence of a limited amount of air. Better yields of 5 are obtained if excess elemental tellurium is present during oxidation, or if the dilithio l,l'-ferrocene ditellurolate is treated with TeCl4. Compound 5 is the last missing member of the l,2,3-trichalcogena-[3]ferrocenophane series Fe(C5H 4E)2E (E = S [5-10], Se [9-13], Te). Pre­ vious attempts to obtain 5 have been unsuccessful [11]. 5 can be isolated as lustrous thin needles which are only slightly soluble in polar organic sol­ vents such as THF, Et20 , CH2C12, CHC13, and to­ luene. The El mass spectrum shows the molecular ion and stepwise elimination of 3 tellurium atoms. The ’H NM R spectra are temperature-dependent, indicating that the molecules of 5 are fluxional and undergo the well-known hindered bridge-reversal movement [7-9 , 14] in solution.